10_linux_bls: don't add --users option to generated menu entries
The generated menu entries have a --users $grub_users option but this will
fail on old versions of GRUB, since it expects the --users option argument
to either be a constant or a variable that has been set.
The latest GRUB version fix this but the GRUB core isn't updated on a GRUB
package update, so this will cause the entries to not be shown in the menu
after a system upgrade.
Since can cause issues and because the entries that weren't generated from
the BLS snippets didn't have the --users option either, just don't add it.
Signed-off-by: Javier Martinez Canillas <email@example.com>